Working in China, for someone coming from the "West", comes with its own unique set of difficulties. The first difficulty, of course, is the language barrier which may be present even if you speak perfect 普通话 （Mandarin, Chinese) as many Chinese people still speak in local dialects. The second is another obvious one, the cultural differences. Cultural differences may not be apparent at first but they creep up on you and can present interesting challenges from time to time. 

The biggest challenge/difficult when working in China may not be these obvious ones but rather these things that we take for granted in the "West". 

1) 24 hour power. Power at all isn't always guaranteed even in the big cities. I know of several technology shops that have regular power outages. How does a tech-company operate without power? answer, it doesn't.

2) Internet access. Yes you have the challenges of the great firewall and the impositions it places but you also massive inconsistencies with the web itself. You may be paying for a 2MB line but there is no guarantee that you are going to get that or anywhere near that. Now when you combine spotty Internet with the fact that most of the Internet is hosted outside of China you get a really bad combination for doing any sort of web related work unless, that is, your web is 100% focused on China, your hosted in China and all of your resources are within China; a highly unlikely scenario even for China-based sites/companies.  

As an example of one of the challenges, I uploaded 100MBs of file to a server in the U.S, the upload was done on a 2MB up/down business class ADSL line. The picture shows my upload times. As you can see one 34 MB file took 2 1/2 hours to upload, at a whopping 3.8KB/s but roughly 2 hours later a 13MB file took only 4 minutes at a, moderately faster, 54.7KB/s. This sort of inconsistency reigns supreme here and its just something that, for the moment, you just have to live with.  

Doing any sort of web-based work in China is, in a word, challenging.